Exclusive: Professional social network LinkedIn has shut down API access to a number of developers for terms of service violations, according to the company. The six developers whose access to LinkedIn’s API include Facebook-focused professional network BranchOut, Monster’s social recruiting app Beknown, brand management app Visible.me, resume service Daxtra, professional reputation manager Mixtent and CRM-Gadget.

The shut down of access for BranchOut and Monster’s similar (and recently launched) app BeKnown are particularly surprising. According to LinkedIn, BranchOut, which has been compared to a LinkedIn for Facebook, violated the network’s API TOS with its plans for a premium enterprise recruiting search tool. Charging fees for access to LinkedIn’s content, is a no-no, says the network.

LinkedIn says that it cut off access to its API for BeKnown because the app was using the LinkedIn APIs to send messages to promote BeKnown (and thus profit from the API). LinkedIn is also concerned that BeKnown will be charging for enterprise services related to the API, similar to BranchOut. Mixtent and Visible.me were also shut down for the same reasons. And CRM-Gadget and Daxtra were both shut down for storing LinkedIn member data.

In the case of BranchOut and BeKnown, it’s hard not to think of the whole Twitter-UberMedia debacle, in which Twitter shut down API access to UberMedia for TOS violations, including trademarks, privacy and monetization violations. UberMedia is a direct competitor to Twitter, with it army of third-party clients.

Likewise, BranchOut (and now BeKnown) are competitors to LinkedIn in some ways. BranchOut, which is backed by Accel, Norwest, Floodgate, and Redpoint, allows you to network and find jobs through your friends on Facebook. The company also allows you to import skills, education, and job history from LinkedIn as well. And the company is allowing brands and organizations to post jobs to users. The startup has been growing in a territory that LinkedIn has not yet invaded—Facebook.

LinkedIn, which has 20,000 developers using its APIs, has been on fairly good terms with its developers minus a few stumbles. In January, LinkedIn shut down access to CubeDuel, a service that mixes the best (or worst) of Hot or Not with the professional social network. Apparently CubeDuel exceeded LinkedIn’s API limits, but it was actually the startup’s fault.

LinkedIn says it is open to reinstating its APIs to these developers and startups if they comply with the network’s TOS. LinkedIn has partnership deals with some developers where startups pay fees for the API (which they can monetize off of).

But LinkedIn could probably learn a thing or two from Twitter’s tenuous situation with its developers, and should definitely navigate these waters very carefully.

Update:

BranchOut issued this statement in response to LinkedIn’s move:

At BranchOut we consider the next generation platform for professional networking to be Facebook. Changes to the LinkedIn API have little impact on the BranchOut experience, as it was only being used by a small fraction of our users. That said, we believe user data should be owned by the user, and that people should be allowed to share their data with the new services and contexts that provide the most utility.

We’ve analyzed our statistics, and it has led to a pretty exciting discovery for us—namely that we are causing a groundswell within a much larger audience than that addressed by the prior generation of career services. BranchOut users encompass not only the professional networker, but also the far larger base of 700 million Facebook users worldwide who would like to use their social graph to help them in business, recruiting, sales, and job search. For example, in addition to white collar professionals, our users are college students, workers in retail, manufacturing, hospitality, military, government, and others who have yet to find a professional voice within a social network. We are excited to be the first to give this larger global audience a relevant professional networking solution.

We are surprised and disappointed by LinkedIn’s decision, which we believe not only goes against the interests of LinkedIn users, but also contradicts what LinkedIn claims to stand for – openness and connectivity. Professional networkers are social in nature and LinkedIn has just limited their ability to connect when and where they want. They’ve taken away users’ rights to control how and when they can share their own profile data and personal contacts. We also note that it was within days of Monster’s launch of BeKnown that LinkedIn decided to block the API when there have been other networking-oriented apps using the API for months.While this move by LinkedIn creates an inconvenience for their users, BeKnown members will continue to build their networks from all the largest online sites including Facebook, Yahoo, Google and Monster.